[The reference intervals of thyroid functional indicators in pregnant population in Xi'an].

To establish reference intervals for thyroid functional indicators in early (T1), mid-term (T2), and late stage (T3) pregnancy in a population of women in Northwestern China. A cross-sectional study was conducted on 620 pregnant women. Subjects were recruited through a questionnaire where apparently healthy women were selected. Serum thyroid stimulating hormone (TSH3), total triiodothyronine (TT3), total thyroid hormone (TT4), free triiodothyronine (FT3), and free thyroid hormone (FT4) were detected using the Beckman Unicel DXI 800 automatic chemiluminescence analyzer (the third-generation TSH detection reagent for TSH3),and the reference intervals of different gestation periods were established. The results showed that the reference intervals of TSH3 in T1, T2, and T3 were 0.05-4.59, 0.61-6.01, and 0.63-4.78 mIU/L, respectively; TT3 were 1.62-2.97 nmol/L, 1.59-2.95 nmol/L, and 1.45-2.70 nmol/L, respectively; TT4 were 95.49-185.00 nmol/L, 92.70-181.54 nmol/L, and 77.93-155.09 nmol/L, respectively; FT3 were 3.18-5.22 pmol/L, 2.78-4.67 pmol/L, and 2.51-4.18 pmol/L, respectively; and FT4 were 7.72-12.97 pmol/L, 6.90-1.09 pmol/L, and 5.63-9.85 pmol/L, respectively. All thyroid function indexes had statistically significant differences between the three stages of pregnancy (TSH:=30.879,<0.01;FT3: =153.827,<0.01;FT4: =229.967,<0.01;TT3: =36.484,<0.01;TT4: =58.531,<0.01). 20 independent samples were collected to verify the reference intervals of TSH, FT3, FT4, TT3 and TT4 for three trimesters of pregnancy, and all of them passed.